A Meta-Analysis of the Effects of Organic and Inorganic Fertilizers on the Soil Microbial Community

In order to investigate the general tendency of soil microbial community responses to fertilizers, a meta-analysis approach was used to synthesise observations on the effects of inorganic and organic fertilizer addition (N: nitrogen; P: phosphorus; NP: nitrogen and phosphorus; PK: phosphorus and potassium; NPK: nitrogen, phosphorus and potassium; OF: organic fertilizer; OF+NPK: organic fertilizer plus NPK) on soil microbial communities. Among the various studies, PK, NPK, OF and OF+NPK addition increased total phospholipid fatty acid (PLFA) by 52.0%, 19.5%, 334.3% and 58.3%, respectively; while NP, OF and OF+NPK addition increased fungi by 5.6%, 21.0% and 8.2%, respectively. NP, NPK and OF addition increased bacteria by 6.4%, 9.8% and 13.3%, respectively; while NP and NPK addition increased actinomycetes by 7.0% and 14.8%, respectively. Addition of ammonium nitrate rather than urea decreased gram-negative bacteria (G–). N addition increased total PLFA、bacteria and actinomycetes in croplands, but decreased fungi and bacteria in forests, and the F/B ratio in grasslands. NPK addition increased total PLFA in forests but not in croplands. The N addition rate was positively correlated with the effects of N addition on gram-positive bacteria (G+) and G–. Therefore, different fertilizers appear to have different effects on the soil microbial community. Organic fertilizers can have a greater positive effect on the soil microbial community than inorganic fertilizers. The effects of fertilizers on the soil microbial community varied with ecosystem types. The effect of N addition on the soil microbial community was related to both the forms of nitrogen that were added and the nitrogen addition rate.